White House Pastry Chef Bill Yosses Talks Desserts at Harvard

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Every lecture attendee got a paper cup filled with a chocolate mouse figurine, a cocoa bean, and an aromatic slice of soft marshmallow.

Updated at 12:27 PM EST on Wednesday, Sep 22, 2010

Last night, hundreds of food nerds (among them NBC New York's The Feast) stood in line outside Harvard’s Science Center, to attend a public lecture on molecular gastronomy and desserts, given by the White HouseExecutive Pastry Chef, Bill Yosses. Yosses’ talk was part of a series of public lectures pegged to a course called Science and Cooking: From Haute Cuisine to the Science of Soft Matter. (Click here for more details and The Feast's coverage.)

Kitted out with little more than a whisk, a few bowls, and a bottle of liquid nitrogen, Yosses executed four recipes—chocolate mousse, meringue, streudel, and liquid-nitrogen olive oil sorbet—to interpret the course’s science principle of the week (that the major components of food are called polymers, which are altered through cooking by changes in temperature and pH).

Yosses at Harvard

Super-geeky tenets of molecular gastronomy aside, here are the notes we jotted down while at Yosses's lecture:

2. A shiny chocolate is a fine chocolate. A shiny surface indicates that it’s been correctly taken through different gradations of temperature that caused the molecules to align in a certain way. When all the molecules are aligned and facing the same way, they reflect light. In chocolate that has not been well-tempered, the cocoa butter molecules migrate to the outside of the form, they don’t line up, and therefore don’t reflect light (or shine).

3.Use food-safe essential oils to fragrance meringue.In the marshmallow meringue Yosses demonstrated, he used gelatin to help the egg whites maintain their shape. To add a flavor or aroma to meringue, Yosses turns to the fragrance industry, specifically to Mandy Aftel of Berkeley, California (http://www.aftelier.com/) for her super-concentrated, food-safe essential oils. “Take the head of a pin and dip it in the oil,” Yosses said, “and start incorporating little by little. It’s learn as you go. Some oils take on a potency with time as they combine with other ingredients.”

4.Read Hervé This's manual called Molecular Gastronomy: Exploring the Science of Flavor, unclog arteries. Yosses took a page from it to create a chocolate mousse using only chocolate, water, and gelatin (no egg yolks or heavy cream).

5. When kneading dough for a streudel, use oil, work it for a long time so the gluten bonds form, and use your knuckles, not your fingertips. Yosses stretched the dough from one edge of the lab table to the other in order to illustrate the malleability of the gluten.